This invention relates generally to non-destructive evaluation of welds and more particularly to a method and apparatus for non-destructive concurrent evaluation of partially completed welds to permit detection and identification of welding flaws during the welding process.
Modern procedures for industrial arc welding of critical parts for such products as aircraft, ships and nuclear power plants normally require non-destructive evaluation of the integrity of the welds and repair of any defects that would impair the use of these parts. In such applications, most welds are produced by making multiple passes in a prepared joint configuration, frequently using mechanized welding equipment and then the completed weld is evaluated using known non-destructive evaluation techniques. The most common prior art techniques utilize radiography employing x-ray techniques and ultrasonics using ultrasonic sound to inspect the interior of the weld. If a weld defect is detected with dimensions in excess of those allowed by applicable codes, as a result of the non-destructive evaluation of the completed weld, the defect must be removed and the weld repaired.
The repair of a defect is begun by exploratory grinding. If the defect is in a deep weld (i.e. covered by subsequent multiple passes) a lot of otherwise good weld deposits are ground out to remove the defect. The part must then be rewelded and the weld reinspected. This process entails high materials energy and labor costs. Many of these costs can be eliminated or dramatically reduced and substantial labor productivity gains could be achieved by a concurrent evaluation system which could detect the flaws soon after they are produced and before they are covered with succeeding weld passes.
In such a concurrent evaluation system it would be highly desirable to be able to detect and distinguish welding flaws; (1) porosity, and (2) lack of fusion. Porosity is the presence of bubbles or pores in the weld metal. Usually some porosity is acceptable depending upon the distance between the bubbles and the overall length of the defect. Lack of fusion occurs when the weld metal does not wet and fuse with the parent metal. Most acceptance codes do not allow any lack of fusion and thus all lack of fusion flaws must be repaired. Hence, it is highly desirable to be able to distinguish types of flaws with any concurrent evaluation system in order to assure that the unnecessary repairs are not made and necessary repairs are made.
It is accordingly an object of this invention to provide a novel concurrent weld evaluation system for near real-time evaluation of partially completed welds.
It is another object of the invention to provide a novel concurrent weld evaluation system utilizing near real-time ultrasonic inspection in conjunction with computerized pattern recognition analysis of ultrasonic echoes.
It is yet another object of the invention to provide a novel concurrent weld evaluation system utilizing pattern recognition analysis of ultrasonic echoes to detect welding flaws in partially completed welds and distinguish types of welding flaws.
It is yet another object of the invention to provide a novel concurrent weld evaluation system utilizing an ultrasonic search head following a predetermined distance behind a automated welder utilizing computer pattern recognition analysis of reflected ultrasonic energy to identify the location of welding flaws and distinguish between types of flaws.
Briefly, according to one embodiment of the invention, apparatus is provided for concurrent non-destructive evaluation of partially completed welds for use in conjunction with an automated welder. The apparatus includes an ultrasonic generator mounted in fixed proximate relationship to the welder for generating pulses of ultrasonic signals and for coupling the ultrasonic signals in real-time to the region of the partially completed weld. In addition, an ultrasonic detector is provided for detecting ultrasonic signals reflected from the region of the partially completed weld and analysis means is provided for processing the detected ultrasonic signals and identifying weld flaws in a response thereto.